ACRIDINE SPECIES ADSORBED ON MODELS OF ATMOSPHERIC PARTICULATE MATTER AND THEIR ROLE IN THE PHOTODEGRADATION MECHANISMS UNDER N₂ OR O₂ ATMOSPHERES

Abstract

Comparing the acridine absorption and fluorescence spectra in solution with those of acridine adsorbed on the atmospheric particulate matter models, the nature of the adsorbed species has been determined. On the surface of ammonium sulfate, the ground and excited state species are protonated acridines. For acridine on silica, alumina, and magnesium oxide surfaces, the hydrogen bonded and/or neutral acridine species were determined to be present. On silica, ground state protonated acridines are also present. On alumina, photoprotolytic reactions are proposed to occur because the emission of the protonated species was observed at 470 nm. The rates of acridine photodegradation on the different surfaces were measured under a nitrogen atmosphere: the observed tendency for these was: (NH_{4 2}SO₄ > MgO > Al₂O₃ > SiO₂. The rates are larger on surfaces were the hydrogen bonded and neutral species exist. Species on (NH₄)₂SO₄ showed an unusually large rate of photodestruction. The rates under an O₂ atmosphere were slower (than under N₂) for acridine on MgO, Al₂O₃, and SiO₂, and equal for acridine on (NH₄)₂SO₄.

Keywords:

• acridine
• atmospheric particulate
• aza-aromatic
• inorganic surfaces
• photochemistry
• polycyclic aromatic compound

Acknowledgments

The authors acknowledge financial support from the Alliance for Graduate Education and the Professoriate (National Science Foundation, HRD9817642) and the Novel Energy Sources (U.S. Department of Energy, DE-FG02-01ER45868) fellowship programs.